Flexible diffusers are conventionally used to support aerobic biological processes in wastewater treatment plants. A flexible diffuser typically comprises a disc-, tube-, or strip-shaped membrane that is constructed of rubber or other similar materials, which is punctured to provide a number of perforations in the form of holes or slits. In operation, pressurized air is sent through these perforations to create a plume of small bubbles. The bubbles rise through the wastewater and provide the surrounding wastewater with the oxygen needed to sustain the desired biological processes occurring therein.
FIG. 1 shows a partially-broken side perspective view of a fine bubble diffuser assembly 100 that is conventionally used in modern wastewater treatment facilities for “submerged” treatment of the wastewater. Wastewater treatment with such assemblies is described in, as just one example, F. L. Burton, Wastewater Engineering (McGraw-Hill College, 2002), which is hereby incorporated by reference herein. When in use, a plurality of diffuser assemblies is arrayed on several lateral distribution conduits that cross a wastewater treatment tank. Diffuser assemblies may, for example, be placed every foot along a given lateral distribution conduit. A blower located near the tank sends compressed air to the lateral distribution conduits via several support pipes (e.g., drop pipes and manifold pipes).
In the diffuser assembly 100, a flexible diffuser membrane 110 sits atop a diffuser body 120. The diffuser body 120 comprises a threaded mating tube 130, an air inlet orifice 140, and a receiving surface 150 for coupling to a retainer ring 160. The retainer ring 160 holds the flexible diffuser membrane 110 against the diffuser body 120. When gas is applied to the flexible diffuser membrane 110 through the air inlet orifice 140, the gas pressure expands the flexible diffuser membrane 110 away from the diffuser body 120 and causes the membrane's perforations to open so that the gas discharges through them in the form of fine bubbles. When the gas pressure is relieved, the flexible diffuser membrane 110 collapses on the diffuser body 120 to close the perforations and prevent the liquid from entering the diffuser body 120 in the opposite direction. Generally, a flexible diffuser membrane 110 configured in this way produces bubbles smaller than five millimeters in diameter. The resultant large ratio of surface area to volume in these bubbles promotes efficient oxygen mass transfer between the bubbles and the surrounding wastewater. The fine bubbles also cause an upward movement in the wastewater tank, which helps to keep solid waste in suspension and to mix the contents of the tank.
A typical wastewater treatment tank may include 2,000 diffuser assemblies and their associated distribution conduits. Because of this large number, the ease in which the diffuser assemblies are mounted (i.e., mated) to the distribution conduits becomes a large factor in determining labor needs and, ultimately, installation costs. One such mounting method, for example, comprises the use of a clam-shell device or saddle that encircles the distribution conduit and provides a mounting point for the diffuser assembly. FIG. 2 shows such a saddle 200 on a distribution conduit 210 with a diffuser assembly 220. To install the diffuser assembly 220, a hole is first drilled in the distribution conduit 210 where the diffuser assembly 220 is to be placed, and then the saddle 200 is encircled about the distribution conduit 210 overlying the aperture and tightened by hammering in a wedge 230. The diffuser assembly 220 is then attached to the top of the saddle 200. Watertight seals are ensured using two internal rubber O-rings (not shown). Another mounting method comprises the solvent welding of a plastic diffuser base to a plastic distribution conduit. The diffuser base and distribution conduit may, for instance, be formed of polyvinylchloride. A bead of resin around the solvent weld further ensures a watertight seal.
Nevertheless, while these mounting techniques are generally effective and are in widespread usage, they tend to be labor intensive and require the presence of a skilled foreman and a semi-skilled crew, which are costly and are not always readily available. These techniques are therefore not always conducive to quick repairs without a lot of prior notice. Accordingly, it is desirable to obtain alternative means of mounting diffuser assemblies to distribution conduits that are less labor intensive than prior art means. Ideally, these alternative mounting means may be performed by less skilled labor, while still providing the same level of reliability in use.